Volume 21, Number 9—September 2015
THEME ISSUE
Emerging Infections Program
Emerging Infections Program
Socioeconomic Disparities and Influenza Hospitalizations, Tennessee, USA
Table 2
Average annual age-standardized and race-stratified incidence of influenza hospitalizations, by neighborhood percentage of households below poverty, household crowding, and percentage of households with female head of household, Middle Tennessee, USA, October 2007–April 2014*
| Characteristic | Hospitalizations, no. (%) | Age-standardized annual incidence (95% CI) | Rate ratio | Rate difference | RII† |
|---|---|---|---|---|---|
| White, n = 1,242 | |||||
| % Below poverty | |||||
| <5.0 | 233 (18.8) | 11.0 (9.6–12.5) | 2.5 (2.0–3.1) | ||
| 5.0–9.9 | 320 (25.8) | 13.6 (12.2–15.2) | 1.2 (1.1–1.4) | 2.7 (0.6–4.7) | |
| 10.0–19.9 | 374 (30.1) | 16.3 (14.7–18.1) | 1.5 (1.3–1.7) | 5.3 (3.1–7.5) | |
| ≥20.0 | 315 (25.4) | 23.0 (20.5–25.7) | 2.1 (1.8–2.4) | 12.0 (9.1–14.9) | |
| Household crowding‡ | |||||
| <5.0 | 1,113 (89.6) | 14.8 (13.9–15.7) | 1.9 (1.3–2.8) | ||
| 5.0–9.9 | 99 (8.0) | 19.1 (15.5–23.2) | 1.3 (1.1–1.6) | 4.3 (0.4–8.1) | |
| 10.0+ | 30 (2.4) | 26.7 (17.9–38.9) | 1.8 (1.3–2.6) | 11.9 (2.2–21.6) | |
| % Female head of household | |||||
| <20.0 | 556 (44.8) | 12.4 (11.4–13.5) | 2.4 (2.0–3.0) | ||
| 20.0–39.9 | 423 (34.1) | 16.9 (15.3–18.6) | 1.4 (1.2–1.5) | 4.5 (2.6–6.4) | |
| 40.0–59.9 | 190 (15.3) | 20.7 (17.8–24.0) | 1.7 (1.4–1.9) | 8.2 (5.1–11.4) | |
| 60.0+ | 73 (5.9) | 32.3 (25.1–41.3) | 2.6 (2.1–3.3) | 19.9 (12.2–27.5) | |
| African American, n = 418 | |||||
| % Below poverty | |||||
| <5.0 | 20 (4.8) | 17.8 (10.7–28.4) | 3.3 (2.2–4.8) | ||
| 5.0–9.9 | 40 (9.6) | 15.9 (11.2–22.6) | 0.9 (0.5–1.6) | −1.8 (−11.4 to 7.7) | |
| 10.0–19.9 | 79 (18.7) | 21.7 (17.1–27.3) | 1.2 (0.8–1.9) | 4.0 (−5.4 to 13.3) | |
| ≥20.0 | 279 (66.7) | 34.6 (30.6–39.0) | 1.9 (1.5–2.5) | 16.8 (7.8–25.8) | |
| Household crowding† | |||||
| <5.0 | 339 (81.1) | 26.3 (23.5–29.3) | 1.8 (1.1–2.8) | ||
| 5.0–9.9 | 64 (14.6) | 33.6 (25.2–44.4) | 1.3 (1.0–1.7) | 7.3 (−2.1 to 16.8) | |
| 10.0+ | 15 (3.6) | 41.3 (22.7–71.1) | 1.6 (0.9–2.7) | 15.0 (−6.6 to 36.7) | |
| % Female head of household | |||||
| <20.0 | 49 (11.7) | 14.8 (10.9–19.9) | 3.6 (2.5–5.1) | ||
| 20.0–39.9 | 77 (18.4) | 20.8 (16.1–26.8) | 1.4 (1.0–1.9) | 6.0 (−0.6 to 12.6) | |
| 40.0–59.9 | 139 (33.3) | 31.6 (26.5–37.4) | 2.1 (1.7–2.6) | 16.7 (10.0–23.5) | |
| 60.0+ | 153 (36.6) | 40.0 (33.8–46.9) | 2.7 (2.2–3.3) | 25.1 (17.5–32.8) | |
*Rates within ethnic subpopulations (i.e., Hispanic) were not calculated because of low numbers for these groups. RII, relative index of inequality.
†RII is calculated as the exponent of the slope of a Poisson regression model by using incidence rate as the outcome variable and the proportion of the population in that socioeconomic group as the predictor variable. The RII can be interpreted similarly to an incidence rate ratio that compares those in the quantitatively highest category with those in the lowest categorization. For example, an RII of 2.5 would indicate a 150% increase in risk when those in the quantitatively highest category are compared with those in the lowest (such as the <49.9% category being compared with the ≥66.0–74.9 category for percentage of patients employed). A low RII with CIs <1 would indicate decreased risk.
‡Household was evaluated for number of persons per room.